This invention relates to the preparation of hexene-1 oligomer by the oligomerization of hexene-1 in the presence of a Friedel-Crafts catalyst and promoter. More particularly, the invention is concerned with the addition of a hydrocarbon solvent, such as n-nonane or saturated hexene-1 oligomer product to hexene-1 in the presence of a boron trifluoride (BF.sub.3) and water catalyst system. Hexene-1 oligomer may be used in very light lubricating oils, more specifically hexene-1 oligomer may be used as an emollient in cosmetic preparations.
A variety of Friedel-Crafts catalysts have been used in the oligomerization of 1-olefins. The use of an aluminum halide and promoter is well known. U.S. Pat. No. 4,066,715 and U.S. Pat. No. 4,219,691 suggest the use of an optional solvent to dilute the reaction mixture as well as achieve easy control of the reaction temperature.
BF.sub.3 -catalyzed oligomerizations of C.sub.6-16 n-.alpha.-olefins are well known. U.S. Pat. No. 3,763,244 employs a water co-catalyst and U.S. Pat. No. 3,780,128 suggests using an alcohol co-catalyst. The use of a solvent is not recommended since this would require the addition of a separation procedure to remove the solvent from the system.
A variety of co-catalysts or promoters have been recognized which are beneficial in BF.sub.3 catalyzed systems. For example, U.S. Pat. No. 4,213,001 describes a process for oligomerizing a 1-olefin having 6-12 carbon atoms or a mixture thereof in a suspension of a powdered solid adsorbent. A two-fold advantage is obtained. The catalyst disposal problem is eliminated and a high trimer yield of product results. In addition to this co-catalyst, the use of an inert solvent is said to be possible. The solvent is said to slow down the various reaction rates. Likewise, U.S. Pat. No. 4,066,715 discloses that a solvent may be used to control the reaction temperature. Also, U.S. Pat. No. 4,219,691 uses a solvent to reduce viscosity and control temperature. There is no disclosure of the use of a solvent with hexene-1.
Surprisingly, it has now been discovered that the addition of a hydrocarbon solvent to a hexene-1 oligomerization reaction in the presence of a Friedel-Crafts catalyst and suitable promoter results in an increased reaction rate and improved yield of trimer product. More particularly, a BF.sub.3 catalyzed oligomerization of hexene-1 proceeds with BF.sub.3 (gas) and BF.sub.3 .multidot.2H.sub.2 O complex in a hydrocarbon solvent at atmospheric pressure to achieve an increased reaction rate and improved trimer yield. A more expensive promoter such as a solid adsorbant or an alcohol is not necessary.